1. Field of the Invention
This invention relates to valves which are useful for controlling the flow of solids-containing or solids-producing fluids, especially corrosive geothermal fluids. In particular, this invention contemplates valves which are resistant to jamming caused by deposits that interfere with the movement of the valve seat.
2. Description of the Art
It is common in the construction of gate valves, ball valves and like valves having movable valve members to employ valve seats that are accommodated in recesses provided in the valve body and which are spring-urged towards the movable valve member to provide a fluid-tight seal between the movable valve member and the valve seat. One difficulty that has been experienced with such valves is that the sediment or deposits that tend to accumulate behind the valve seat interferes with the movement and the position of the valve seat. Such interference causes the sticking of the movable valve member and inadequate sealing. In certain instances the sediment or deposits behind the valve seat will cement the movable valve member and valve seat together. The cemented or frozen valve in such cases may be freed only with great exertion or destruction of the valve. Alternatively, the valve may have to be disassembled to free such frozen movable member.
In geothermal service wherein corrosive fluids are moved through valves, there is a special tendency for the brine to deposit behind the O-rings and crystallize out as salt. Crystallized salt is an especially effective cement and therefore geothermal service valves are especially difficult to design.
In the valves useful in the transport of petroleum products the sedimentation problems have been to some extent overcome by providing sediment guards to prevent the unnecessary accumulation of sediment in the valve seat recess.
In U.S. Pat. Nos. 3,121,533, 3,972,405 and 4,364,544, sediment guards are described for use in valves utilized in transport of petroleum products. In certain of these patents the sediment guards are stationary whereby they function to simply retard the deposit of sediment in seat recesses. With such stationary sediment guards, sediment eventually gets behind the valve seat. In other of the above references the sediment guards are flexible whereby contact is maintained between the valve seat and the seat recesses by virtue of the expansion and contraction movement of the sediment guard. However, these flexible sediment guards are fabricated from polymeric materials which typically have an adverse reaction to corrosive fluids, such as geothermal brine.
It therefore would be desirable to provide a valve having a guard that is not subject to deterioration in the presence of corrosive fluids and does not merely retard, but eliminates the deposition of sediment in the valve seat recesses.
Therefore it is one object of this invention to provide a valve which is useful in the presence of solids-containing or solids-producing fluids, especially corrosive fluids and in which valve materials that are subject to corrosion are not in contact with said corrosive fluids.
It is another object of the instant invention to provide a valve which eliminates the deposition of sediment between the valve seats and the seat recesses.
It is another object of this invention to provide a valve useful in the presence of flowing geothermal brines, which valve is not subject to freezing by deposition of salt from said brine in the space between the valve seats and the seat recesses.
It is another object of the instant invention to provide a spring-biased, floating or movable valve seat for use in a valve utilized in controlling the flow of corrosive fluids wherein said valve seat is easily installed in such valve and the spring is protected from freezing in the presence of corrosive fluids.
Other objects and advantages of the instant invention will be apparent after a careful reading of the specification below: